Filtration is a technique which is becoming increasingly important in the purification and manufacture of protein-containing materials. Many of these materials are intended for use in pharmaceutical preparations and are of high economic value. Filtration is used in many of the steps in the production of these materials. The process is also used in analytical and diagnostic determinations. Thus, in many instances filtration may be employed to separate proteins from biological fluids which also include materials such as cells, cell debris, or residues of animal or plant tissue. Filtration, and particularly ultrafiltration, can be used to separate desired proteins from other biological materials or to adjust solutions to a useful protein concentration. The technique also finds application in the final stages of producing pharmaceutical or biological preparations where sterilization of the product is accomplished by removing bacteria and other biological organisms from the preparation.
Since filtration may be conducted several times during the manufacture or purification of a protein-containing preparation, it is important that the filtration procedure result in losses of as little of the desired protein as possible from the fluid being filtered. This is especially important when the proteins sought are difficult to produce and are very costly. It is also important when filtration is the final operation performed on a bottling line in the manufacture and packaging of pharmaceuticals, where each bottle must contain a specified amount of the desired materials and little or no loss of protein during filtration can be tolerated.
While some studies of the adsorption of proteins on various surfaces have been conducted, the construction of filtration systems which have a reduced tendency to adsorb protein has been given very little attention. Most research has been directed to filtration media which have a low affinity for protein. Although the use of such media can reduce the adsorption of desired protein during a filtration process, the problem of losses of protein due to the adsorption of protein by other components of the filtration system which contact the protein-containing fluid during use has not previously been considered.
Most of the materials currently used to construct filtration systems or diagnostic devices employed in the filtration or testing of biological fluids suffer from their tendency to sorb protein-aceous materials. Although materials exist which demonstrate a low affinity for proteinaceous materials, they typically have shortcomings other than the adsorption of proteinaceous materials. Thus, some materials may be difficult to fabricate into the desired component because of difficulties in molding, machining, etc. Other materials, although easier to fabricate, may be very expensive. Still other materials which do not suffer from these problems may not be satisfactory in applications relating to the production of pharmaceutical materials. For example, such materials may not withstand sterilization or autoclaving conditions or may be incompatible with other components of the pharmaceutical preparations.